Catalyst 4006/Sup III High CPU

We have a Catalyst 4006 with a supervisor III that experiences high CPU (80-90%+) for periods of about 20 minutes. We are running IOS version Version 12.2(25)EWA14. We are running 2 OSPF processes on the box. One of the OSPF processes is running in a VRF (VRF Lite). I have checked traffic on the interfaces during the high CPU event and have seen nothing out of the ordinary. There have been no changes to the config that correlate with the start of the CPU spikes. During the high CPU SSH to the box is responsive. Based on the stated config/harware/ios; does anyone have any suggestions for things to check to try to pinpoint what is causing the high CPU?

There are a couple of causes of this but first lets see if due to icmp redirects the cpu is spiking when there is more traffic.

I don't know if this is your case but normally the 4500 is the default-gateway for the hosts/servers and then you have some routers/firewalls on a separate vlan than the hosts that the 4500 redirects the traffic to.

Do you have routers/firewalls on the same vlan(subnet) than heavy traffic users or servers, if so, the 4500 may be sending icmp redirects back to the hosts so they use the router/firewall as the next-hop instead of the 4500. If this is the case then you can disable redirects on the interface vlans of the 4500

We do have "no ip redirects" configured on the interface vlans. The 4000 does serve as the gateway for most of the networks in this area. The gateway is an HSRP address between 2 4000's. The routers/firewalls for these networks are on seperate VLANs.